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NGC 2617
Galaxy in the constellation Hydra From Wikipedia, the free encyclopedia
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NGC 2617 is a Seyfert galaxy in the equatorial constellation of Hydra. It was discovered on February 12, 1885, by French astronomer Édouard Stephan.[7][8] In 1888, Danish astronomer J. L. E. Dreyer described it as "extremely faint, very small, 2 very faint stars involved".[9] It is located at an estimated distance of 202 million light years.[2] In the infrared, the galaxy has an angular size of 0.693 by 0.652 arcminutes.[5]
This is an almost face-on spiral galaxy with a morphological classification of Sc,[4] indicating a spiral galaxy (S) with loosely wound spiral arms (c). In 1992, NGC 2617 was shown to be an extragalactic source of X-ray emission,[10] and in 1996 it was identified as a Seyfert 1.8 galaxy by E. C. Moran and associates.[11] A radio counterpart was found in 1998.[12]
During April 2013, a dramatic outburst was discovered at the core of NGC 2617,[13] and the spectral type was found to have changed to a Seyfert 1. An increase in X-ray emission was observed, followed by an increase in ultraviolet and then infrared luminosity.[4] This event can be modeled by X-ray radiation heating the accretion disk orbiting a supermassive black hole (SMBH) at the center of the galaxy. This was followed by emission at longer wavelengths from the heated disk.[4] An increase in luminosity between 2010 and 2012 may have cleared away dust in the inner part of the disk prior to the outburst, allowing a clearer view and changing the Seyfert type of the galaxy.[14] The SMBH has an estimated mass of 30.9+11.8
−8.5 million M☉.[3]
Additional outbursts were observed from 2016 to 2018, in between deep minima.[15]
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